Io and Jupiter from Voyager 1

Voyager 1 captured this mosaic on Io on March 4, 1979, as a nearly full-phase Io appeared to travel across Jupiter's terminator. Viewed near the edge of its disk and at local dusk, only the uppermost blue hazes of Jupiter's atmosphere are visible.

NASA / JPL / Ted Stryk

The mosaic, which consists of four clear-filter images followed by violet, blue, orange, and green frames, is a great challenge to assemble because in the 11 minutes it took Voyager to record and transmit the 6 images (from 22:36:35 to 22:47:48) Io completely transited the terminator, and because the color frames are not complete, with pieces of Io cut off. Source images can be downloaded here.